Can you customize system notification text?

Today: No. Some time in the future: Yes.

I think it'd be nice to be able to customize that message, based on the current category, maybe user group, trust level.

Can I ask, what's your use case? How would you like to change the text, what would the new text be? — You'd like the same text in the whole forum, or different, per category? And / or something else?

(Temp workaround: You can hide it, with custom CSS.)